Water Budget for the Kohala Area, Island of Hawaii

Ground-water recharge is estimated as the residual component of a monthly water budget calculated using long-term average rainfall, streamflow and pan evaporation data, and soil and vegetation characteristics. The water-budget components are defined seasonally, through the use of the monthly water budget, and spatially by topographic and geologic areas, through the use of a geographic information system model.

The long-term average ground-water recharge for the Kohala area, estimated by water-budget analysis for the topographic areas used in the analysis, is 162 Mgal/d in area A (south windward Kohala), 41 percent of average rainfall; 60 Mgal/d in area B (north windward Kohala), 33 percent of average rainfall; and 24 Mgal/d in area C (leeward Kohala), 13 percent of average rainfall.